The prosecution has opened its case against a man accused of murdering South Australian woman Yasmin Sinodinos in 1991.

Timo Pasanen, 44, was arrested in February last year.

The Supreme Court heard the victim, 25, from Mount Gambier was beaten to death and her body found in a pile of garden rubbish at Anstey Hill in north-eastern Adelaide by a couple whose car stalled on a dirt track.

Prosecutor Sandi McDonald said Pasanen's DNA had been matched to semen found on the victim and on fabric loosely tied over her face.

She also said a witness would tell the court Ms Sinodinos was picked up by a man in a silver Sigma before she died and the accused drove such a car at that time.

"She had been beaten to death and dumped under the pile of garden rubbish [and] left there until someone happened to stumble across her body," she said.

Ms McDonald said the accused man was a university student who was a bit of a loner and lived in a caravan, while the victim was a single mother.

"[They] lived very different lives, they existed in different worlds, but somehow tragically in the hours leading up to her death their paths crossed, the accused had sex with her, he killed her," the court was told.

Defence lawyer Greg Mead said he would not dispute the accused man had sex with Ms Sinodinos, but he said the man had not killed her.